Fix unable to save descriptions for non-leaves.
Misc improvements.

* Ask whether to save changes if any on exit.
* Align labels for fields to the left.
Remove incomplete doxygen comments.
Add doxygen documentation.
Add doxygen documentation.
Add doxygen documentation.
Add zlib.h include.
Add some unit tests.
Make it case insensitive and add MS Office file types.
Remove status bar and associated code, doesn't work anyway.
Fix program asking to save on exit even though we saved manually.
Remove unneeded/unused code.